


To Give Full Growth (to That Which Still Doth Grow)

by MoMoMomma, Rrrowr



Category: Fantastic Beasts and Where to Find Them (Movies)
Genre: Accidental Voyeurism, Anal Sex, Blow Jobs, Bottom Original Percival Graves, Dirty Talk, Exhibitionism, Loss of Virginity, M/M, Masturbation, Praise Kink, Pre-Movie(s), Semi-Public Sex, Sibling Incest, Threesome, Underage Sex, Voyeurism
Language: English
Status: Completed
Published: 2017-03-11
Updated: 2017-03-11
Packaged: 2018-10-02 13:33:32
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,607
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10219436
Author URL: https://archiveofourown.org/users/MoMoMomma/pseuds/MoMoMomma, https://archiveofourown.org/users/Rrrowr/pseuds/Rrrowr
Summary: Theseus had described Percival in extensive detail. Newt had learned all about how Percival was funny and charming, a quiet and thoughtful sort of fellow with a strong desire to prove himself to his father. As the letters grew more effusive, Newt began to imagine someone rather bookish, with a hidden temper that was difficult to light—someone who wasn't ambitious by nature, but who was nevertheless quite strong and mostly level-headed.Newt was happy that his brother had found someone like that. Someone who would serve as a counterbalance to his brother's brashness. Someone who could weather Theseus' endless string of ideas and soak up all the attention that Theseus tended to bestow on anyone that happened to be close by.None of those letters had fully prepared Newt for coming home to this.





	

Newt remembered the first time that he ever saw Percival Graves. 

Percival had been the _American_ friend that Theseus had met over spring. Apparently, Percival had been visiting bits of Europe as he explored some of his family history, of which he was quite proud, and had run into Theseus at a pub in Wales. He and Theseus were similar in age, and so naturally they got on like thieves, according to Theseus' letters. Theseus had described Percival in extensive detail, thanks to his enthusiasm for a new friendship. Newt had learned all about how Percival was funny and charming, a quiet and thoughtful sort of fellow with a strong desire to prove himself to his father. As the letters grew more effusive, Newt began to imagine someone rather bookish, with a hidden temper that was difficult to light—someone who wasn't ambitious by nature, but who was nevertheless quite strong and mostly level-headed. 

Newt was happy that his brother had found someone like that. Someone who would serve as a counterbalance to his brother's brashness. Someone who could weather Theseus' endless string of ideas and soak up all the attention that Theseus tended to bestow on anyone that happened to be close by.

None of those letters had fully prepared Newt for coming home to this.

||

It was Theseus' voice that drew Newt up the stairs, eager to see his big brother after the long train ride from Hogwarts. Their parents were still unpacking the shopping in the kitchen, and Newt snuck quietly up the stairs, hoping to surprise Theseus. He stalled, however, when he found the door to Theseus' bedroom wide open, sunlight spilling into the hall and onto the toes of Newt's shoes. 

Theseus was laughing, whispering into someone's ear. "That's it, Perce," he said softly. "Take what you need."

Newt swallowed thickly and held himself very, very still. He shouldn't watch. This was surely a private moment, but— but they had left the door open for a reason, hadn't they?

Theseus and Percival were still clothed, mostly, but past Theseus' shoulder, Newt could see the curve of his brother's arse moving in a slow, shallow rhythm above his loosened belt. Percival was crushed under Theseus' weight, fingers digging into the bed spread as he panted. All that Newt could see of Percival was his black hair and half his reddened face below it. Past that, Percival's shirt had been pulled open at the collar, exposing his neck and shoulders, at which Theseus took great pains to bite. 

Quiet and thoughtful, Percival might be under normal circumstances, but it was different when he was getting fucked, apparently. He moaned. He grunted. He gasped. And while every noise seemed to be squeezed into near silence by the tightness of his throat, there were times when it had to be smothered by his own fist.

Even then, Newt could make out the strained, "please," that slipped past Percival's fingers.

"I know," Theseus soothed and sat up, shushing Percival's complaints with a heavy hand against the back of his neck. "I was only waiting for the right moment, sweetheart."

Newt held his breath, folded hands pressing against his erection, as Theseus hauled Percival's up by the hips. Theseus smoothed a hand up Percival's back, shoving his shirt up as he went, and folded his fingers over the well-bitten slope of Percival's shoulder. Their rhythm got faster, harder—each beat marked out by a steady _slapslapslap_ that had Newt whimpering as he fought against touching himself.

"Thes, fuck," Percival groaned, low, reaching back—not to slow Theseus' thrusts, but to haul him in tighter. 

"There you go," Theseus crowed softly, triumphant as Percival arched underneath him. "Beautiful."

"Newton!" shouted his mother from the bottom of the stairs. Newt jerked out of Theseus' and Percival's sights. "I'm not taking your trunk to your room for you!"

"Coming!" Newt shouted back, flinching at his word choice, and scrambled down the stairs as quickly as he could—as loudly as he could, just in case there were any doubts about his not being anywhere near the open door to Theseus' bedroom. 

Thankfully, his trunk still had the levitating charm on it, so it was easy to push up the stairs. He did so slowly, stomping heavily on each step, and by the time he passed Theseus' room, his brother was already fully dressed and leaning on the door frame. Behind him, though, Percival was glaring at the buttons of his shirt and appeared to be struggling with a firm bit of wrinkling.

"Hey, little brother," Theseus greeted, reaching out to scrub at Newt's curls. "Long time, no see. C'mere." 

He drew Newt into a long hug, squeezing him tightly around the shoulders. Newt returned it loosely, not wanting to seem clingy, and wrinkled his nose at the smell.

"Gross," he griped. "You stink."

“That’s the all natural scent of man,” Theseus teased, hauling in Newt tighter and seeming to relish in the grunt it caused. “I know you’ve been trapped around adolescent stink for far too long in those common rooms, you may have forgotten. Go ahead, smell to your tiny heart’s content.”

“Get off,” Newt snapped, wiggling to free himself from the clasp, Theseus hanging on gamely for a moment before releasing him.

There was a split second of hesitation where they both just stared at one another, re-familiarizing themselves with a face they hadn’t seen in far too long, before Theseus smiled softly and curved his palm over Newt’s shoulder.

"There's someone I'd like you to meet," he said, guiding Newt into the room. "This is Percival Graves."

Newt stuck his hand out politely, doing his best to overlook the fact that Percival's shirt was wrinkled all over and missing buttons at the throat. "Nice to meet you," he said.

Percival took Newt's hand easily. He didn't even have the grace to look frazzled, although he did shoot Theseus a dirty look. "Likewise," he said. "Theseus has told me so much about you already. I feel like we've known each other for a while."

"Good thing, eh, brother?" Theseus asked, nudging Newt's arm. "We'll be here all summer. What do you think?"

Newt thought that was a terrifying idea. He could barely look either of them in the eye as it was. He didn't imagine that he'd be any better at it tomorrow. What if he caught them having sex again? It was too embarrassing to even contemplate.

He plastered on a smile, though. "Sounds great!"

"Yes," agreed Percival as he tugged firmly at the hem of his shirt. Finally, the wrinkles ironed themselves out with a snap of magic. "I'm sure we'll become wonderful friends."

"I hope so!" Theseus declared brightly. "After all, if I'm going to have to share you with other people, I can think of no one better than Newt!"

||

The second time it happened, Newt got the sneaking suspicion it wasn't an accident. Because it was one thing to fuck in a room, on a bed, even with the door open. This... This was something else.

Their parents were out, so it was understandable that maybe Theseus thought they wouldn’t be caught, that caution could be thrown to the wind. This was not caution in the wind. This was one giant screaming _fuck off_ at the world, and Newt couldn’t help but think Theseus had a plan no one else was privy to.

Because they had walked right past Newt. Theseus had even stopped to lean annoyingly atop his head and complain in a mockingly wistful voice about how he remembered “the horrendous torture” that was summer homework and how he didn’t “envy you one bit, little brother. Do enjoy your summer killing studies.” They’d left him alone after Newt landed one lucky swat on Theseus’ ribs, then wandered over to the study whose doors opened into the dining room Newt was currently stuck in. 

Theseus had lived in this home longer than Newt. He knew exactly how much of the study could be seen from Newt’s vantage point at the table. 

Why in the bloody hell hadn't he closed the doors? 

It was an exquisite type of torture to try and focus on History of Magic homework with _that_ going on not more than twenty feet from him. Newt could hear every soft groan and wet suck without concentrating very hard, and it only seemed amplified when he turned his head and actually saw what was happening.

Theseus was sitting on the settee, leaning back, sprawled like a king with his legs wide open and arms reaching along the back. He didn’t have much choice in it, however. Percival had shoulders broader than Newt originally thought and fitting them between Theseus’ thighs split them open in an unabashed spread. Newt couldn’t see his brother’s cock—thank Merlin for that—but it was mostly because Percival seemed content to keep every single inch in his mouth. 

What Newt _could_ see was Theseus’ hands, tangling in Percival’s hair, keeping him tugged in close.

Newt stood abruptly, pushing back from his homework, stomping over to the study with the intention of giving Theseus a piece of his mind. Because this? This game Theseus was apparently happy to play—a far cry from the games of tag they'd played on the grounds as children—was going to put Newt into the hospital before the summer was up.

The heart could only take so much stress.

He stopped in the doorway, glaring at Theseus until the other met his eyes, resisting the urge to cover where his cock was thick in his trousers, tenting the material. No need to give his unrepentant older brother anything else to tease him about.

“Oh Merlin, sorry, brother.” Theseus drawled, all lazy lidded gaze and slow roll of his hips like Percival’s mouth suddenly did something wicked. “Did we interrupt your studies?”

Percival didn’t seem bothered by the sudden acknowledgement of an audience, doing something that made Theseus groan and tug him in closer by his hair, thighs shaking on either side of him. Newt heard a moan slip out, deep and slick and muffled in a sinful way, and Percival’s hands came up to grasp at the sides of Theseus’ shirt.

“Shouldn’t you be doing this in—in private or something?” Newt was proud of the way he sounded only slightly breathless, like this wasn’t affecting him in the way it so obviously was.

Theseus merely offered a pleasure drunk smirk in his brother's direction. “Ah, you know how it is.” No, no, Newt did not, actually. “Sometimes you can’t—oh _fuck_ , darling, yes, just like that—you can’t be bothered to wait. Not for good things.”

The praise seemed to work for Percival, and Theseus’ whole body shuddered as his head tipped back, hands scrambling to grab onto the back of the settee. Newt got the arguable honor of watching his own brother come, hips jerking up to meet the slick sounds of Percival swallowing, and he felt his cock jerk in sympathetic sensitivity when Theseus suddenly reached down to tug Percival away. He drew him up into a kiss, and Newt absolutely failed to look away when Theseus locked eyes with him over Percival’s shoulder.

He wasn't speaking to him, directing his words to Percival’s finely trembling form, but Newt couldn’t help but think some of it was meant for his ears anyhow.

“So good, sweetheart. Your mouth is just, _fuck_ , s’work of magic. I almost feel guilty, keeping such a sweet thing all to myself.”

||

It happened a third time. A fourth. _A fifth._ It was driving Newt insane. He woke up each morning with his parents already gone to work and dreaded the torture of getting out of bed. He knew now what was bound to happen each time he left his room. They were going to be out there, doing whatever they wanted, _wherever_ they wanted, without caring that Newt would be watching.

Newt scrubbed his face roughly, bracing himself for the coming day. He couldn't even say he wasn't excited by the prospect! They were beautiful together! It was the worst!

 

There was a sudden thump from the wall by Newt's head, and then a wail. Newt just about ran into the next room in worry until he realized that the noises were in a now-familiar rhythm.

"Fuck," he cursed, head falling back to his pillow with a soft thump. 

It sounded like Percival was moaning right against he wall he shared with Newt. He was louder than usual. Theseus, too, seemed like he was no longer restraining himself to merely murmured praises. Newt listened to them fuck, pressed his ear to the wall so that he could hear Percival's heavy breathing, and though he could not hear the smack of their hips meeting, there was still the thump of the bed to foster Newt's imagination.

He could picture it just fine after weeks of watching them. He could perfectly see the flush of their skin, both of them broad men, tight with lean muscle. They were always so beautiful together—each of them a marked contrast to the other. Percival with his perpetual paleness burning savagely in summer sun and his stark black hair. A severe painting that melted like water color into the sun-kissed gold of Theseus' arms as he tossed back his his curls and yanked Percival onto his cock.

Newt guiltily shoved a hand into his pajama pants and touched himself as the vibrations from the wall shook against his brow. A part of him wanted to be in the same room as them, wanted to watch them touch each other freely without feeling like he was also intruding. He moved his hand to the beat of Percival's noises and thought about what it might be like to be the reason for them—what it might be like to be in Theseus' stead. He had to hold himself back several times, force his hand off his cock just to keep from coming too soon. 

Then he heard it. Percival's shaky moan, shaping out the sound of Newt's name.

"Say it again," Theseus urged.

"Newt," Percival groaned. "Please!"

A slapping noise hit high on the wall—perhaps Theseus' palm—and Newt stared at the pale blue paint of his bedroom as he heard his brother say, "D'you hear that, little brother? He's crying for you."

They started up again almost at once but with more vigor—the bed banging against the shared wall almost viciously, Percival mewling so loudly that it was almost like having it right in his own ear. Newt bit his lip as he stripped his cock, lost in the dizzying idea of Percival actually wanting him, and by the time his come was spilling across his palm, the other side of the wall was silent.

After that, Newt avoided them for a while as best he could. He stayed in his room to do his homework or he visited his mother's hippogriff stables or walked around the neighborhood if they started fucking where he could hear them. It was boring (except for the hippogriffs) and a little lonely (again, except for the hippogriffs), but still better than being teased about his crush by a brother he'd always admired. Worse still, there was the hazy dreams he woke from each morning, where he didn't even know if he dreamed about Percival or Theseus. He used to know. Not so much anymore. The only certain thing was the guilty evidence in his underwear—proof of the filthy desires that haunted him.

Dinners became uncomfortable. Their parents sensed the tension, and his mom came to talk to him once. Though Newt promised to tell her if something was wrong, he couldn't imagine how he would explain what was going on between him, his brother, and his brother's boyfriend, even if he wanted to. 

Newt wanted— He... He wanted. And everywhere he turned, Theseus was leaning into Percival's space, speaking softly as he looked at Newt in the distance. If it wasn't the two of them together, it was Percival alone—most notably curled up in the bay window, catching Newt's eye above the brim of his book before blushing softly. Or it was Theseus returning indoors from his morning run, stripping off his sweaty shirt in the mud room, and then, when he noticed Newt standing a short distance away, stripping off his shorts too.

He was determined not to make a big deal out of it, but eventually, it seemed that Theseus wasn't going to let the issue fester any longer.

||

Newt absolutely just intended to ask Theseus a question about a defensive spell. Because, in all honesty, DADA had never been Newt’s best class, and Theseus had gotten top marks in it. But Newt found the question—and all words entirely—slipping away from his mind like quicksilver when he stepped into the doorway.

Percival was on his stomach, a sheet laid far too low on his hips to be considered helpful or decent, the curve of his arse visible just over the stretch of silver fabric. He was snuggled into the pillow, head turned towards where Theseus was sprawled next to him, the sheet thankfully higher on his own hips.

“Baby brother!” Theseus greeted him happily, waving one hand lazily in a come-hither gesture. “What brings you to my room this amazing day?”

Sex dumb was a good look on Theseus too. Irritatingly enough. 

“I... had a question.”

“I have questions too.” Theseus propped himself up on his elbows, grinning over at Percival before turning his attention back. “Important questions.”

“Like what?” Newt shifted uncomfortably in the doorway, mentally threatening his cock with horrible punishments if it continued to take interest in the scene before him.

“Is my darling little sibling still a virgin?”

“Theseus.” Percival’s low, amused groan was overlaid with Theseus’ happy laugh. “Be nice to him.”

“I’m only asking for his own sake! He’s a growing boy, after all. It’s normal to start experimenting.” Theseus turned his attention back to Newt. “And have you?”

“I...what?”

“Are you still a virgin?” Theseus’ gaze was sharp, something predatory in the depths, and Newt suddenly felt like he was being pinned in place.

His mouth was dry, his legs refused to move from their place on the floor, and he found himself murmuring a “yes” without permission from his brain. Newt flushed upon realizing what he'd just admitted, forcing himself to run when Theseus’ shocked laugh rang through the room. 

“Oh, no! No, come back here!” There was the mutter of a spell, and Newt grabbed fruitlessly for the doorjamb as he was yanked towards the bed.

Theseus had _always_ excelled at wandless magic.

Unfortunately.

He slid to a stop mere inches from the side of the bed and nearly toppled onto it, inches from his brother’s face when Theseus leaned up. A strong hand captured his chin and forced him to meet Theseus’ gaze, the click of his throat when he tried to swallow loud in the sudden silence. 

“Nothing?" Theseus asked disbelievingly. "Not a single ‘helping hand’ for my little brother? No eager young thing fumbling under the covers with you in the dead of night?”

“N-No.” Newt twisted against the grasp half-heartedly, body heating from the proximity and the questions in Theseus’ baritone growl. He was also achingly aware of Percival's dark gaze against the side of his face, but Newt did not dare to even glance in Percival's direction.

“You’ve never even had your cock sucked?" Theseus thumbed over Newt's lower lip. "No pretty darlings eager to test out skills they read about in one of those insipid gossip magazines?”

“I don’t really... No one has offered,” Newt murmured weakly. 

Theseus clicked his tongue in disapproval. “Oh that just won’t do.” He let go, thankfully, and flopped back onto the bed with a huff.

Newt rolled his eyes at the dramatics when Theseus made a scene of tapping his finger on his chin, humming while he thought. “I mean, as a caring big brother, it’s practically my job to guide my brother through the best experiences of his life. To ensure he's well taken care of, naturally.” His eyes darted to where Percival had twisted onto his side and was arching an unamused brow at him. “I’m tempted to suggest _you_ do it, Percival. Merlin knows you’re talented enough to make it good for him. But we wouldn’t want to spoil him on his first go round.”

“Every first blowjob is enough to spoil someone,” Percival said, raking his eyes over Newt, and Newt shuddered, almost physically feeling the caress. “I wouldn’t mind, you know. You’re adorable.”

“That’s that settled then!” Theseus grinned broadly and, before Newt could protest or even make a noise of confusion, reached to grab him by the back of his shirt and tumble him onto the bed.

He landed half over Theseus, nearly smacking his nose into Percival’s hip, and immediately tried to scramble back up and away. It was an effort neatly halted when Theseus switched his grip from Newt's shirt to his trouser leg, swinging him more fully onto the bed. Newt wound up on his stomach, sandwiched between them, afraid to move or push himself away in fear of touching the wide expanses of naked skin at his sides.

His cock was only barely behaving. Touching either of them at this point might just break him.

“Get your kit off,” Theseus commanded, scooting up and back until he was resting against the headboard, not bothering to take the sheet with him.

Merlin’s beard...he knew Theseus was, er, well built. But to see it so close up, so unabashed when Theseus spread his legs and settled into the position…

“Come on, Newt," he urged, smacking the top of one thigh lightly, grin still firmly in place. “Strip down and come sit between big brother’s legs. Best to have someone hold you, I think. You look like you’re about to shake out of your skin.”

“This isn’t precisely what I expected when I came here,” Newt hissed, pushing himself up onto his hands and knees and falling back to the familiar pattern of arguing in this decidedly unfamiliar situation.

“You don’t have to,” Percival said at his side, pushing up to sit. His expression was kind when Newt looked over. “It was an offer, one that you don’t have to take us up on.”

“We won’t push you into anything you don’t fully consent to,” Theseus interjected, looking serious for the first time. 

“But—” Percival swiped a tongue over his lower lip and plucked at the buttons of Newt's shirt as he leaned in. “If it helps you decide any, I’d really like to.”

Newt lost time between him dumbly nodding and when all his clothes come off, snapping back to attention when he settled his back against Theseus’ broad chest. He wondered idly how he looked, twitchy and pale and no doubt scrawny compared to Theseus’ more well-built form, but Percival didn't seem to find it unappealing, if the way his cock was half-hard between his thighs was any indication.

“Relax.” Theseus urged, rubbing warm palms down Newt’s arms when Percival arranged himself between their spread thighs. “You’ll enjoy this, I promise. I could leave though...if it would help?”

Newt grabbed for Theseus' thigh, digging his fingers in as Percival ran gentle fingertips up the sensitive insides of his legs. “No. P-Please. Stay.” 

Honestly, Newt was more terrified by the prospect of facing Percival alone than he was put off by his brother's dick pressing against the slope of his back. And Theseus was right, after all. Newt really did feel like he was about to shake out of his skin, and as Percival stretched past the arch of Newt's cock to lay a soft kiss on his hip, Newt became increasingly grateful for the solidity of Theseus' body, the strong bracket of his legs framing him in.

"Still okay?" Percival asked. 

Newt nodded enthusiastically, and embarrassingly, he jerked away from Percival in shock when he got a long sweep of tongue along the length of his cock. Newt tried very hard to stay still while Percival's head bobbed between his legs, but it was hard—so hard—when the thin strands of his hair slipped to tease at Newt's skin. Percival's reddened lips stretched obscenely around his length. His tongue curled along the head, poked out to wet his balls. Such simple things and yet, they were the most glorious, most devastating things that Newt had ever felt.

Theseus gentled him, arms wrapped around Newt's torso and hands stroking down the center of his chest. "He's good, isn't he?" he whispered against Newt's temple. "I taught him everything he knows."

Percival hummed in confirmation, pulling off when Newt's hips hitched upward helplessly. He was smiling when the tip of Newt's cock slipped from his mouth to smack at his belly. "I dunno," he drawled roughly. "I think my enthusiasm more than makes up for whatever it is you think you have left to teach me, Thes."

"Enthusiasm?" Newt squeaked.

Percival moaned against the underside of Newt's cock, sucking it down with a steadily increasing determination until his lips were wrapped around the base and his throat was fluttering tightly around the tip. He swallowed again and again, pulling back only far enough to get an easy breath before sinking down again. Newt mewled, digging his fingers under Theseus' knees. His hips jerked helplessly, little twitches that got nowhere because Percival was already taking it all, and his breath came with these whining sobs, which he did his best to smother in the curve of his brother's throat. 

Even then, even when he could feel the inevitable end approaching, Newt wished it wouldn't end. Still, he came with a terrible, torn sound and was left panting and embarrassed as Percival sucked him clean. The afterglow wasn't as horribly awkward as he feared. The seconds dragged out between one moment and the next, and the only thing that Newt could think was that Percival was beautiful.

He lounged quite happily between Newt's knees, smiling smugly to himself. He even sounded rather cheeky when he said, "My Scamander Brothers."

Percival rose up on all fours, leaning in to kiss over Newt’s chest before seeking out Theseus' mouth. They kissed languidly, like old lovers, and Newt was amazed at the lack of jealousy he felt. There was no sour bile pooling in his mouth, no twist to his stomach that felt like a knife. There was just a quiet and peaceful sense of satisfaction. He could see them, if he only twisted his head to the side, and the sight was as pleasing to the eye as any work of art. Theseus was golden, just like him, and the contrast between his skin and Percival’s disheveled black hair made Newt sigh softly, breaking the silence of the room. 

“I think someone else might appreciate a kiss,” Theseus murmured against Percival’s mouth, hand cupping his jaw and turning him toward Newt with a gentle push.

Newt was unexpectedly face to face with Percival, and he didn't know if it was Theseus’ quiet suggestion or the languid pleasure still curling through his form that made him lean forwards. Percival kissed him like he was something precious, like he was something breakable, and Newt opened his mouth on a moan. There was a taste on Percival’s tongue, something dark, and Newt wondered for a moment if he was tasting himself...or Theseus.

Either way, he found he truly didn't mind.

**Author's Note:**

> This is a bit of a backstory for a longer fic that we are working on. Posted this to see what people might think of the idea, if yall are interested in seeing more of where this would go, so please let us know!


End file.
